The porphinedione structure of heme d1. Synthesis and spectral properties of model compounds of the prosthetic group of dissimilatory nitrite reductase.

Chang, C. K.; Wu, Wenyuan

doi:10.1016/s0021-9258(19)84419-8

Cited by 62 publications

(27 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Not only the low-intensity visible and near IR MCD bands but also the EPR g -values of iron chlorins ,− and proteins that contain them , are very similar to those of [(TMP)Fe(4-CNPy) 2 ]ClO 4 32a and cytochrome bd 32b from Escherichia coli and ( ii) the iron dioxoisobacteriochlorin of heme d 1 , the prosthetic group of the dissimilatory nitrite reductases of denitrifying bacteria as well as ( iii) the siroheme prosthetic group of bacterial sulfite and nitrite reductases …”

Section: Introductionmentioning

confidence: 77%

π-Acid Ligands in Iron(III) Porphyrinates. Characterization of Low-Spin Bis(tert-butylisocyanide)(porphyrinato)iron(III) Complexes Having (d_xz,d_yz)⁴(d_xy)¹ Ground States

et al. 1996

View full text Add to dashboard Cite

The synthesis and characterization of isocyanide complexes of (porphyrinato)iron(III) species, [(Porph)-Fe(t-BuNC) 2 ]ClO 4 , Porph ) OEP, TPP, are reported. The crystal structures of [(TPP)Fe(t-BuNC) 2 ]ClO 4 and [(OEP)-Fe(t-BuNC) 2 ]ClO 4 have been determined. Consistent with the expected effect from the strong π-acceptor character of the axial tert-butyl isocyanide ligands, the X-ray structure of the complex shows that the porphyrinate ring is strongly ruffled. The spectroscopic properties of these complexes suggest the possibility of "blurring" of the definitions of the electron configurations of low-spin Fe(III) macrocycles having (d xy ) 1 electronic ground states, with the extreme possibilities being low-spin Fe(III)-(macrocycle) 2-, with the unpaired electron localized in the d xy orbital of the metal, and low-spin Fe(II)-(macrocycle) 1-• , with the unpaired electron localized on the macrocycle. EPR spectroscopy of the TPP and OEP complexes shows that the g-values (g ⊥ ) 2.20-2.28, g | ) 1.94-1.83) are consistent with an electron configuration that is (d xz ,d yz ) 4 (d xy ) 1 , the purest (d xy ) 1 ground state system with the most complete quenching of orbital angular momentum discovered thus far (∑g 2 as small as 13.5). Proton NMR spectra of [OEPFe(t-BuNC) 2 ]-ClO 4 in CD 2 Cl 2 , recorded over the temperature range -100 to +37°C, also support the (d xy ) 1 ground state, where ruffling of the porphyrinate ring makes it possible for unpaired electron spin delocalization to the 3a 2u (π) orbital of the porphyrinate ring. This orbital has very large electron density coefficients at the meso positions and hence explains the very large negative contact shift of the meso-H; its size indicates considerable (∼19%) spin delocalization from low-spin Fe(III) to the 3a 2u (π) orbital by porphyrin f Fe π donation. Mössbauer and IR spectral data are also consistent with the (d xy ) 1 ground state.

show abstract

Section: Introductionmentioning

confidence: 77%

π-Acid Ligands in Iron(III) Porphyrinates. Characterization of Low-Spin Bis(tert-butylisocyanide)(porphyrinato)iron(III) Complexes Having (d_xz,d_yz)⁴(d_xy)¹ Ground States

et al. 1996

View full text Add to dashboard Cite

show abstract

“… Low-basicity pyridines and other strong π-acceptors as axial ligands in six-coordinate iron(III) porphyrins (ferrihemes) result in a (d xz ,d yz ) 4 (d xy ) configuration of the iron(III) center as opposed to the usual (d xz ,d yz ) 3 (d xy ) configuration. Density functional calculations have been used to characterize and visualize these variable electron distributions.…”

mentioning

confidence: 99%

“…Six-coordinate iron porphyrinoids occur at the active sites of a variety of biomolecules such as the cytochromes b and the enzymes containing the so-called green hemes. , Depending on the nature of the axial ligands and of the porphyrinoid, the electronic configuration for the iron(III) oxidation state can range from (d xz ,d yz )(d xy ) 2 to (d xz ,d yz )(d xy ) 1 , leading to a wide variation in the NMR, EPR, and Mössbauer properties of these molecules. − There are also interesting stereochemical questions involving these molecules. Why is the macrocycle ruffled in nearly all six-coordinate low-spin iron(III) porphyrinoids but flat in analogous Fe(II) complexes?…”

mentioning

confidence: 99%

Theoretical Studies of Low-Spin Six-Coordinate Iron(III) Porphyrins Relevant to Cytochromes b: Variable Electronic Configurations, Ligand Noninnocence, and Macrocycle Ruffling

1999

View full text Add to dashboard Cite

Low-basicity pyridines and other strong π-acceptors as axial ligands in six-coordinate iron(III) porphyrins (ferrihemes) result in a (d xz ,d yz )4(d xy ) configuration of the iron(III) center as opposed to the usual (d xz ,d yz )3(d xy ) configuration. Density functional calculations have been used to characterize and visualize these variable electron distributions. For the (d xz ,d yz )4(d xy )1 configuration, the porphyrin ligand is strongly noninnocent and has significant a2u-type cation radical character due to d xy −“a2u” interactions. These orbital overlaps may be a significant driving force for porphyrin ruffling. Another factor that favors ruffling appears to be the small ionic radius of low-spin iron(III), with the result that all the ferrihemes studied are significantly ruffled, regardless of electronic configuration.

show abstract

“…Compound 2 was synthesized from octaethylporphyrin (Chang, 1980) and the Fe chelate prepared (Chang et al, 1980) as previously described. Compound 3 was synthesized (Chang & Wu, 1986b) from mesoporphyrin and the Cu chelate prepared by addition of cuprous acetate.…”

Section: Methodsmentioning

confidence: 99%

Evidence that heme d1 is a 1,3-porphyrindione

Chang¹,

Timkovich²,

Wu³

1986

Biochemistry

View full text Add to dashboard Cite

Heme d1 is the noncovalently associated heme prosthetic group of the bacterial nitrite reductase known as cytochrome cd1. Additional evidence has been obtained in support of a dioxoisobacteriochlorin, or 1,3-porphyrindione, skeleton for this heme. The new data include the natural abundance 13C NMR spectrum of the free base methyl ester derivative of d1, mass spectrometric determinations of the molecular mass of the free base methyl ester and the Cu and the Zn chelates, visible and 1H NMR spectral comparisons between d1 and synthetic porphyrindione model compounds, and the isolation and characterization of several byproducts formed during the purification of the free base methyl ester of d1. The accumulated evidence strongly supports the following structure for the skeleton of d1: 1-oxo-2-methyl-2'-acetyl-3-oxo-4-methyl-4'-acetyl-5-methyl-6-acrylyl+ ++-7- propionyl-8-methylporphyrin.

show abstract

The porphinedione structure of heme d1. Synthesis and spectral properties of model compounds of the prosthetic group of dissimilatory nitrite reductase.

Cited by 62 publications

References 11 publications

π-Acid Ligands in Iron(III) Porphyrinates. Characterization of Low-Spin Bis(tert-butylisocyanide)(porphyrinato)iron(III) Complexes Having (d_xz,d_yz)⁴(d_xy)¹ Ground States

π-Acid Ligands in Iron(III) Porphyrinates. Characterization of Low-Spin Bis(tert-butylisocyanide)(porphyrinato)iron(III) Complexes Having (d_xz,d_yz)⁴(d_xy)¹ Ground States

Theoretical Studies of Low-Spin Six-Coordinate Iron(III) Porphyrins Relevant to Cytochromes b: Variable Electronic Configurations, Ligand Noninnocence, and Macrocycle Ruffling

Evidence that heme d1 is a 1,3-porphyrindione

Contact Info

Product

Resources

About

The porphinedione structure of heme d1. Synthesis and spectral properties of model compounds of the prosthetic group of dissimilatory nitrite reductase.

Cited by 62 publications

References 11 publications

π-Acid Ligands in Iron(III) Porphyrinates. Characterization of Low-Spin Bis(tert-butylisocyanide)(porphyrinato)iron(III) Complexes Having (dxz,dyz)4(dxy)1 Ground States

π-Acid Ligands in Iron(III) Porphyrinates. Characterization of Low-Spin Bis(tert-butylisocyanide)(porphyrinato)iron(III) Complexes Having (dxz,dyz)4(dxy)1 Ground States

Theoretical Studies of Low-Spin Six-Coordinate Iron(III) Porphyrins Relevant to Cytochromes b: Variable Electronic Configurations, Ligand Noninnocence, and Macrocycle Ruffling

Evidence that heme d1 is a 1,3-porphyrindione

Contact Info

Product

Resources

About

π-Acid Ligands in Iron(III) Porphyrinates. Characterization of Low-Spin Bis(tert-butylisocyanide)(porphyrinato)iron(III) Complexes Having (d_xz,d_yz)⁴(d_xy)¹ Ground States

π-Acid Ligands in Iron(III) Porphyrinates. Characterization of Low-Spin Bis(tert-butylisocyanide)(porphyrinato)iron(III) Complexes Having (d_xz,d_yz)⁴(d_xy)¹ Ground States